Titou

x.py

import pygame

pygame.init()

# 1 = en haut à droite
# 2 = en bas à droite
# 3 = en bas à gauche
# 4 = en haut à gauche

l_écran = 400
h_écran = 300

direction = 2

x1 = 0
y1 = 0

x2 = 30
y2 = 60

screen = pygame.display.set_mode((l_écran,h_écran))

while True:

    screen.fill((0,0,0))
    
    pygame.draw.line(screen, (255,0,0), (x1,y1), (x2,y2), (7))
    
    pygame.display.update()
    
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            pygame.quit()
            
    if direction == 1 and y1 <= 0:
        direction = 2
        
    elif direction == 1 and x2 >= l_écran:
        direction = 4
        
    elif direction == 2 and y2 >= h_écran:
        direction = 1
        
    elif direction == 2 and x2 >= l_écran:
        direction = 3
    
    elif direction == 3 and y2 >= h_écran:
        direction = 4
        
    elif direction == 3 and x1 <= 0:
        direction = 2
    
    elif direction == 4 and x1 <= 0:
        direction = 1
        
    elif direction == 4 and y1 <= 0:
        direction = 3
            
            
            
    if direction == 1:
        x1 += 3
        y1 -= 3
        x2 += 3
        y2 -= 3
    elif direction == 2:
        x1 += 3
        y1 += 3
        x2 += 3
        y2 += 3
    elif direction == 3:
        x1 -= 3
        y1 += 3
        x2 -= 3
        y2 += 3
    elif direction == 4:
        x1 -= 3
        y1 -= 3
        x2 -= 3
        y2 -= 3
        
    
    pygame.time.delay(100)